What hormone promotes the contraction of uterine muscles during childbirth?

Oxytocin is the key hormone involved in promoting the contraction of uterine muscles during childbirth. It is produced by the hypothalamus and released from the posterior pituitary gland. During labor, oxytocin levels rise, stimulating the smooth muscle of the uterus to contract, which helps initiate and regulate the process of labor. These contractions aid in the movement of the baby through the birth canal.

Progesterone plays a different role in pregnancy by maintaining the uterine lining and promoting a suitable environment for fetal development, and its levels decrease as labor approaches. Estrogen also participates in various stages of pregnancy and helps prepare the uterine muscles for contractions, but it does not directly cause the contractions during labor. Prolactin is primarily involved in milk production after childbirth rather than in the contraction of uterine muscles during labor. Thus, the unique function of oxytocin makes it the correct answer for promoting uterine contractions during childbirth.